Units in families in Robot and Revit

[Karol_Piroska]

Just wondering if anyone came across this one and what was their solution:

I have imported Robot model into Revit. I had to add many other beams and columns in Revit that do not need to be in Robot for calculation purposes. Now when I wanted to create Material takeoff / steel tonnage I realised that the families in Robot include units but families load into Revit (the ones included when installing Revit) do not have units. It was therefore impossible to get the total tonnage:

- the calculation would work only for one or the other family, depends which W you include in the formula

- as both weight parametrers are represented as "W" and you cannot have two formulas

As well trying to add formula with the loaded family seems akward as it tells you the units do not match even if you have nothing else just W in the formula. Adding smth like W*2 would give you units J/g (even tho W is unitless).

The only way around it I found was to export W as shared parameter from the Robot family, delete W in Revit family and add the shared one. Obviously now I had to ammend this value for each beam/column type.

Does anyone know other possibly easier solution?

Thank you

[sureshchotrani]

Kindly check here

[okapawal]

There is inconsistency.

Families created by Robot contain W parameter which is "Mass per Unit Length" discipline, so for example kg/m unit.

Families from the standard content contain W parameter which is "Number" discipline, which means they are unitless.

I was thinking about conditional formula, but indeed calculated values don't work if you have both W parameters in one schedule.

Simply, a formula doesn't know which one to use.

Another workaround, similar to yours, is to create another shared parameter and use it in both cases.

1. Create new WW parameter of "Mass per Unit Length" discipline.

2. In case of Robot created families you add WW to the family.

Assign formula WW = W

3. In case of the standard families you add WW to the family.

Assign formula WW = W *(1 kg) / (1 m)

This converts units from unitless to mass/length !

Now you've got consistent, schedulable WW parameter for both cases.

I know it's also tedious workaround, but you don't need to amend values for each type.

[Karol_Piroska]

Thank you Waldemar,

I didnt realise you posted reply. I'll try that, hopefully it will work for all the other revit standard families where the weight has different name as well, eg Nominal weight that is in kgf/m. 

But honestly speaking one would say that something like units and names of parameters should be a standard mainly if it comes from one company so that we are not mixing apples and pears.

Thanks again for the workaround, appreciate that.

Regards

Karol

[okapawal · Accepted solution]

Right, it shoud be more consistent.

Pay attention that Nominal Weight is (kgf/m) a force/length value.

If you want to get mass you need to divide by acceleration unit.
So in this case will be:

WW = Section Shape: Nominal Weight * (1 s) ^ 2 / (1 m)

[Karol_Piroska]

Hi Waldemar,

I havent had a chance to test it properly till now. It kind of works but the results are not what I would expect and it definitely doesnt look like rounding to me. Any idea why the two values are different? 

Thank you

[Karol_Piroska]

nevermind .. realised the formula should be more like "Nominal Weight * (1 s) ^ 2 / (9820 mm)"